docs: def _setSmsMemory(self, readDelete=None, write=None):
          """ Set the current SMS memory to use for read/delete/write operations """
          # Switch to the correct memory type if required
          if write != None and write != self._smsMemWrite:
              self.write()
              readDel = readDelete or self._smsMemReadDelete
              self.write('AT+CPMS="{0}","{1}"'.format(readDel, write))
              self._smsMemReadDelete = readDel
              self._smsMemWrite = write
          elif readDelete != None and readDelete != self._smsMemReadDelete:
              self.write('AT+CPMS="{0}"'.format(readDelete))
              self._smsMemReadDelete = readDelete